An Etymological Dictionary of Astronomy and Astrophysics

The quality or quantity of force, power, resistance, etc. → line strength.
Mechanics: The ability of a material to resist → stress without yielding or fracture.

Etymology (EN): M.E., from O.E. strengþu “power, force, vigor, moral resistance,” (cf. O.H.G. strengida “strength”), noun of strong.

Etymology (PE): Zur “strength,” variant zâvar; Mid.Pers. zôr “strength, power, vigour,” zâvar “strength, force,” zôrik “powerful,” loaned in Arm. zaur; Av. zāvar- “strength.”